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proc: consoles: document console_lock usage

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The console_lock is held throughout the start/show/stop procedure
to print out device/driver information about all registered
consoles. Since the console_lock is being used for multiple reasons,
explicitly document these reasons. This will be useful when the
console_lock is split into fine-grained locking.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-11-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2022-11-16 17:27:22 +01:06 committed by Petr Mladek
parent d25a2e748a
commit 8b5dd40088
1 changed files with 9 additions and 0 deletions
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9
fs/proc/consoles.c
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@ -63,6 +63,15 @@ static void *c_start(struct seq_file *m, loff_t *pos)
struct console *con;
loff_t off = 0;
/*
* Take console_lock to serialize device() callback with
* other console operations. For example, fg_console is
* modified under console_lock when switching vt.
*
* Hold the console_lock to guarantee safe traversal of the
* console list. SRCU cannot be used because there is no
* place to store the SRCU cookie.
*/
console_lock();
for_each_console(con)
if (off++ == *pos)